This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Pressure sensitive labels are multi-layered constructions that include a pressure-sensitive adhesive, and are used to label articles by applying pressure to the label when it is in contact with an article to adhere the label to the article via the pressure-sensitive adhesive. Such pressure sensitive labels are popular because, among other characteristics, they are versatile, and allow for a high level of printability with bright colors printed on surfaces. Further, they can be printed onto a large spectrum of materials such as paper, foil, metal, plastic, and other synthetic materials. They are also compatible with a wide array of finishing processes, including (but not limited to) perforating, embossing, and hot stamping.
Referring to FIG. 1, a typical prior art pressure sensitive label 1 is shown. When labeling an article with a pressure sensitive label, one generally acquires a base pressure sensitive label stock 2 from a separate supplier. The base pressure sensitive label stock 2 usually includes at least four laminated layers: (1) a carrier 3 (sometimes referred to as a “liner”), (2) a release layer 4 disposed onto one surface of the carrier, (3) an adhesive layer 5 (including a pressure-sensitive adhesive) disposed onto the release layer, and (4) a face stock 6 disposed onto the adhesive layer.
The typical base pressure sensitive label stock 2 can thus be thought of as having a support portion 7 (carrier 3 and release layer 4) and a transfer portion 8 (adhesive 5 and face stock 6). The release layer 4 is used to allow the portion that will transfer to an article to peel away and release from the carrier 3 during label application.
The face stock 6 is typically made from a web or sheet of paper, film, or foil, and is applied or laminated to the adhesive layer 5 sequentially at some time after the adhesive layer 5 has been laid down. Once the base pressure sensitive label stock 2 is acquired from a supplier, the face stock 6 may then be printed on with an ink layer 9 or layers (text, graphics, indicia, etc.) to create the label decoration and information. The conventional pressure sensitive label construction is then applied to an article surface by removing the carrier 3 and release layer 4 to expose the adhesive layer 5 and placing the adhesive layer 5 into contact with the desired surface and applying pressure, to transfer the adhesive 5, face stock 6, and ink layer 9 to the article (the “ink layer” as described herein may include more than one ink to create the appearance of the label decoration and information).
While these pressure sensitive labels are well known, there are many drawbacks to the use of the above-described pressure-sensitive labels. As described above, the initial base pressure sensitive label stock (carrier, release layer, adhesive layer, and face stock) is generally provided by a third party with the label design (i.e., ink graphics, text, indicia, etc) being added thereafter. This does not allow for the construction of an entire label (e.g., carrier, release layer, adhesive layer, face stock, and ink layer) at one location and/or time. And so, present pressure sensitive labels require a multi-location, multi-step process for their production, thereby lengthening the amount of time needed to manufacture a completed pressure sensitive label. (When the “construction of a label,” or the like, is referenced herein, it is intended to refer to both the construction of an individual label and/or to the construction of a web of multiple individual labels.)
Further, the supplier of the base pressure sensitive label stock does not know ahead of time what size shape, contour, etc. of ink layer indicia will be printed on the base stock to create the final web of labels (the “web of labels” being a length of base pressure sensitive label stock with multiple individual labels printed via ink/indicia along its length). Thus, the base pressure sensitive label stock is created with a flood coating of adhesive and a face stock that matches or generally closely matches the area of the carrier (to accommodate any size, shape, contour, etc. of ink layer or layers that may be printed, and any size, shape, and/or contour of label or labels). Because of this, following printing of the ink design, the web of labels must be die cut to produce the final web (carrier/release with individually cut labels thereon). This process requires that the carrier be made of a strong material—such as a polyester—so that it can withstand the die cut process without being cut itself (as only the ink layer, face stock, adhesive, and release gets cut). The cut matrix that does not include labels is then removed and discarded. The use of the strong material (e.g., polyester) of the carrier presents the problem that the carrier cannot be recycled, as the material cannot be placed into the recycle stream for label web materials. While the carrier is commonly polyester, that does not prevent the use of other materials for the carrier (such as a paper liner, glassine, polypropylene, or blends of such materials).
Further, because the base pressure sensitive label stock needs to be provided by a third party with printing of the ink layer occurring thereafter, it is required that the layers of the final label be ordered in such manner that the adhesive is proximal to the carrier (e.g., adjacent to the release layer) with the ink disposed distal from the carrier. This configuration results in further drawbacks to the pressure sensitive labels of the prior art. First, the fact that the adhesive is proximal to the carrier requires a release layer or coating between the carrier and the adhesive to allow the adhesive, face stock, and ink layer to release from the carrier during application to an article. The need for this release layer adds materials, and thus cost, to these conventional pressure sensitive labels. Second, the positioning of the ink layer distal to the carrier means that the ink layer will be the outer surface of the label once it is applied to an article. This means that the ink layer can be easily scuffed or damaged—disrupting the aesthetic appearance of the article. This also means that metallics cannot be used as inks in these conventional pressure-sensitive labels (due to their ease of damage). Thus, the inks that can be used in these labels are limited, and the designs are subject to damage. One could add a protective layer to the label (to the outside of the ink layer) but, like the release layer described above, this adds yet another layer, and cost, to the label.
Further, where the label is to be adhered to a contoured or irregular surface, and where a high degree of flexibility is desired, the rigidity of the face stock (and any rigidity due to the multiple layers of the label) may interfere with the application and the adherence of the label.
Further still, one common occurrence in the application of a pressure sensitive label is to have various defects, such as wrinkles and blisters. These defects occur when the label becomes misaligned to the article to which it is applied, and/or entrapment of air between the label and the article. The result is less than optimum visual appeal (poor aesthetics), label failure due to scuffing or tearing of the unsupported label, or even unsellable products.
In view of many of the drawbacks of pressure sensitive labels, as described above, (particularly the many layers that are needed, the use of a third party base construction, and the damage that can occur to the label indicia), many have often turned to heat transfer labels as an alternative type label. Heat transfer labels are desirably resistant to abrasion and chemical effects in order to avoid a loss of label information and desirably possess good characteristics of adhesion to the articles to which they are affixed.
Heat transfer labels are multilayered constructions, with each layer having its own function. For example, heat transfer labels generally include an adhesive layer, an ink layer, and a release layer. The release layer may be a wax release layer, and is often directly adjacent a carrier sheet, such as on a roll or web of labels. Thus, in such an example, the label may be thought to include a “support portion” (e.g., carrier sheet and release layer and a “transfer portion” (i.e., ink layer and adhesive layer). When subjected to heat, the wax release layer melts, thereby allowing the transfer portion to be separated from the carrier sheet, and the adhesive layer adheres the ink layer to an article being labeled. Alternatively, all or part of the wax release layer may transfer as well, to provide protection to the ink layer. Additionally or alternatively, the labels may include a separate protective layer overlying the ink layer to protect the ink layer from abrasion.
More specifically, in the heat transfer labeling process, the label-carrying sheet is subjected to heat, and the label is pressed onto an article with the ink layer making direct contact with the article. As the paper sheet is subjected to heat, the wax layer begins to melt so that the paper sheet can be released from the ink layer. (And, as described above, a portion of the wax layer may be transferred with the ink layer and a portion of the wax layer may remain with the paper sheet.) After transfer of the ink layer to the article, the paper sheet is removed, leaving the ink layer firmly affixed to the article. In an alternate embodiment, where the wax layer also transfers, the wax layer thus may serve two purposes: (1) to provide release of the ink layer from the sheet upon application of heat to the sheet, and (2) to form a protective layer over the transferred ink layer. After transfer of the label to the article, the transferred wax release layer may be subjected to a postflaming technique which enhances the optical clarity of the layer (thereby enabling the ink layer therebeneath to be better observed) and which enhances the protective properties of the transferred wax layer.
However, the primary drawback to the use of the heat transfer label is the requirement of heat to be applied during the labeling process, which may not be desirable. It is, therefore, desirable that a pressure sensitive label construction be constructed for use as a label, for example, which avoids the need to use a conventional face stock formed from paper, film, or foil. It is further desirable that the pressure sensitive label construction have printability, convertibility and dispensability properties that are better than or equal to that of pressure sensitive label constructions of the prior art (as described above). It is also desirable that such a pressure sensitive label construction be designed in a manner that reduces the amount of manufacturing time needed to complete same, when compared to a pressure sensitive construction of the prior art. Further, it would be desirable to reduce and/or eliminate wrinkles and/or blisters that may form during label application. Further, it would be desirable for such a pressure sensitive label construction to have reduced layers, and thus cost, increase recyclability, increase ease of application to an article being labeled, and reduce the incidence or likelihood of damage to the ink layer.